Common Insect and Mite Pests of the Greenhouse

Comments (0)

Transcript of Common Insect and Mite Pests of the Greenhouse

Common Insect and Mite Pests of the GreenhouseWhy?Control Measures?Species?A greenhouse provides the perfect environment: warm, humid conditions and abundant food supply with few (if any) predators.CulturalPhysicalBiologicalChemicalWe are going to take a closer look at the following:WhitefliesAphidsThripsSpider MitesFungus GnatsLeafminersThere are many, many more pests - but these are the most common/problematic in a greenhouse.WHITEFLIESSilverleaf WFGreenhouse WFPlants attackedFeed on > 500 species of plantsEx: poinsettia, hibiscus, gerbera daisy, verbena, garden mum, salviaDamage SymptomsFeed by injecting enzymes and sucking out the sap; Feed on underside of leaves;Reduce plant vigor (stunted growth);Chlorotic spots (yellowing);Honeydew (excrement) causes sooty mold, which interferes with photosynthesisBiological Controls2 parasitic waspsEncarsia formosa(develops within the W.F. nymph)Adult feeds on blood from the wound(more effective against silverleaf W.F.)It is important to control W.F. populations very early - once they are established, they are very hard to control.AphidsPlants attackedAphids will attack nearly all greenhouse plantsDamage SymptomsYoung leaves are stunted, curled;SpotsHoneydew, sooty mold;Cast skins;Virus vectorBiological ControlsPredatorsParasitic WaspsPathogensGreen lacewingLady beetlePirate bugGenus AphidiusBeauvaria bassiana - an insect-pathogenic fungi (AKA: Entomopathogen)Spider MitesDamage SymptomsLeaves of affected plants show this distinct spotted effect, known as "stippling"This happens when the spider mites tear into the plant tissue to feed on the sap - this causes the leaf cells to ruptureSpider mites can also spin webbingThe easiest way to sample for spider mites:- Sharply tap suspected leaves over white paper- Look for green, red, or yellow specks the size of a grain of pepperBiological ControlsPirate bugs are also effectiveMites in the family Phytoseiidae (orange) are predators of spider mites.ThripsDamage SymptomsWhite spotsStipplingDistortion of leaves and flowersEarly flower maturityFlower discolorationVirus transmission (Impatiens Necrotic Spot Virus - INSV)In addition to sucking the plant's juices, adults and larvae scrape plant tissues to induce the flow of juices. This causes the tissue to dry out and enlarge to form silvery patches.Biological ControlsThere are a lot of options, but there isn't 1 method that works completely. Predators, such as the pirate bug and predatory mites must be fast moving if they are going to feed on thrips. Pathogens, such as B. bassiana, can also work.Fungus GnatsDamage SymptomsThey thrive on overwateringLarvae feed on roots, which lead to less root vigor and increased disease incidencesBecause this equates to reduced H2O and nutrient uptake, the plant will show signs of stunted growth and yellowingAdults spread detrimental fungal spores throughout the greenhouse through defecationBiological ControlsBeneficial Nematodes (genus Steinernema)Also, predatory mites are effective.LeafminersDamage SymptomsAdults: puncture leaf and feed on juicesLarvae: feed on interveinal tissuesThe mines themselves are the primary damage: unslightly and reduce overall plant health.Biological ControlsThese parasitic wasps find larvae in the mines, penetrate the leaf tissue, and lay an egg directly on the larvae.Dacnusa sibiricaDiglyphus isaeaIn addition to sucking the plant's juices, adults and larvae scrape plant tissues to induce the flow of juices. This causes the tissue to dry out and enlarge to form silvery patches.Cultural controls are practices that reduce pest establishment, reproduction, dispersal, and survival. For example, changing irrigation practices can reduce pest problems, since too much water can increase root disease and weeds.Physical controls kill a pest directly or make the environment unsuitable for it. Examples include mulches for weed management, steam sterilization of the soil for disease management, or barriers such as screens to keep birds or insects out.The easiest way to sample for thrips:- Use blue sticky cards/insect traps (thrips are attracted to the blue color; most other insects are attracted to yellow)Now it's your turn to identify these common greenhouse and agricultural pests!